Extraction cell for a centrifugal partition chromatograph, a centrifugal partition chromatograph containing such a cell, and a method for producing such an extraction cell

ABSTRACT

An extraction cell ( 10 ) for a centrifugal partition chromatograph ( 20 ), which extraction cell ( 10 ) contains an extraction chamber ( 12 ) delimited by a cell wall ( 12   c ) and accommodates the liquid stationary phase ( 30   á ), and it has a liquid inlet opening ( 13   b ) and a liquid outlet opening ( 13   k ) serving to let in and out the liquid mobile phase ( 30   m ) to be made to flow through the extraction cell ( 10 ). The extraction cell ( 10 ) contains an extraction chamber ( 12 ) established as a tubular body, and a liquid inlet plug ( 16   b ) that includes a liquid inlet opening ( 13   b ) and a liquid outlet plug ( 16   k ) that includes a liquid outlet opening ( 13   k ), that can be attached to the extraction chamber ( 12 ) and an insert ( 14 ) through which liquids may pass is positioned in the extraction chamber ( 12 ) between the liquid inlet opening ( 13   b ) and the liquid outlet opening ( 13   k ). A further objective relates to a centrifugal partition chromatograph ( 20 ) containing such an extraction cell ( 10 ), and a method for providing such an extraction cell ( 10 ).

The object of the present invention relates to an extraction cell for acentrifugal partition chromatograph, which extraction cell contains anextraction chamber delimited by cell walls, and has a liquid inletopening and a liquid outlet opening, and an insert through which liquidsmay pass is positioned in the extraction chamber between the liquidinlet opening and the liquid outlet opening.

The object of the invention also relates to a centrifugal partitionchromatograph containing such an extraction cell.

The object of the invention also relates to a method for providing suchan extraction cell.

Chromatography is the collective name for mixture separation methodsbased on multistage, high-efficiency, quasi-balance processes, whichtoday, among separation technology processes, has become one of the mostfrequently used analytical methods. The fields of application includepharmaceutical analysis, foodstuff industry, toxicology andenvironmental analysis tests.

The basis of the procedure is that the components in a mixture to beseparated are distributed in different proportions between a stationaryphase and a mobile phase (eluent) flowing through the stationary phasein a specific direction. Using this method the molecules, ions of thecomponents may be selectively separated from each other from solutionswith complex compositions. Separation is made possible by that theindividual components travel at different speeds while the mobile phaseis flowing. This speed depends on the degree of interaction between thecomponent and the stationary phase. Therefore, the components of themixture travel at different speeds because their distribution betweenthe stationary phase and the mobile phase, in other words theirpartition coefficient is different.

During centrifugal partition chromatography the liquid stationary phaseis kept in place by a strong centrifugal field. In this technique, asseen in the block diagram in FIG. 1 a , the chromatograph contains aliquid pumping system 102 serving for feeding the mobile phase 30 m, asample feed unit 104 serving for feeding the mixture material 106 to beseparated, a rotor 24 that rotates around an axis, a detector 110 andfraction collection system 112. A product 114 leaves the system as thefinal result of the separation process, which preferably contains asingle component of the mixture 106. In the rotor 24 a network ofserially connected extraction cells 10 connected to each other byconnection tubes 18 ensuring liquid connection rotates around the axisof the rotor 24. The separation process takes place in the cascade ofseries-connected extraction cells containing an inlet and an outletopening, which are rotated around a common axis at a given speed. As aresult of the pumping the mobile phase enters the cell containing thestationary phase through the inlet opening and breaks up into tinydroplets. The resultant of the centrifugal force and the buoyancy willbe exerted on the tiny droplets of the mobile phase, due to which thedroplets will flow through the stationary phase. The two phases comeinto contact with each other over a large surface area within the cell.Near to the outlet opening the two phases are separated from each otherand the mobile phase leaves the cell.

Coriolis force appears in the reference frame of the cells due to therotation, as a result of which the path of the mobile phase is diverted.Using liquid simulation methods it can be demonstrated that the Coriolisforce reduces the efficiency of the mixing of the two phases, as thediverted droplets run down the sidewall, so reducing the contactinterface. The Coriolis force causes circular flow and remixing in thecell, which is a strongly degrading factor from the point of view ofseparation (see FIG. 1 b ).

Various methods may be found in the literature for the production ofextraction cells. The Partitron centrifugal partition chromatographprotected by the patent with registration number U.S. Pat. No. 6,913,692consists of a titanium cylinder, in which the extraction cells and thechannels connecting them are produced by milling. A special CNC millingmachine is required as the device is milled inside and outside from asingle titanium alloy cylinder. The titanium alloy used is veryexpensive and during machining a large part of the cylinder goes towaste. Therefore the manufacturing of the device is expensive andresults in a great deal of waste. The milled channels and cells areconnected by covering plates, with flat seals being used between them.The material of the flat seals according to the specification isfluoroelastomer (Viton), which, however, does not tolerate the organicsolvents used for cleaning the device well. When they come into contactwith these they swell, soften and their sealing ability lessens.

Patent document with registration number U.S. Pat. No. 4,968,428presents a stacked plate chromatograph in which the network of cells andchannels is machined into a stainless steel plate. Teflon sealing platesare to be found between the stainless steel plates, which are puncturedat the locations where flow is to take place between the plates. Thegreatest disadvantage of the arrangement is that the ratio of the usefulvolume as compared to the total mass of the device is very low, and themachining is expensive, as a great deal of waste is produced duringmachining. A further disadvantage of the plate arrangement is that dueto the Teflon seals used its pressure resistance is low, and after timethe Teflon plates become deformed, so reducing pressure tightness. Inorder to perfectly clean the device it must be completely disassembled,which is complicated and only possible with a press.

The aim of the invention is to provide an extraction cell, a centrifugalpartition chromatograph containing such an extraction cell and a methodfor the production of such an extraction cell that is free of thedisadvantages of the solutions according to the state of the art, inother words to be able to provide an extraction cell at a low cost inwhich the effect of the Coriolis force occurring may be effectivelyreduced. The aim of the invention is also to provide an extraction cellwhich may be manufactured so as to cause less waste than the solutionsaccording to the state of the art.

The invention is based on the recognition that the extraction cell maybe produced with the help of a tubular body shaped extraction chamber,and a liquid inlet plug and liquid outlet plug connected to its ends,during the production of which less waste is produced and the ratio ofuseful internal volume/mass is much greater as compared to the solutionsaccording to the state of the art. It was also recognised that an insertthat liquid may flow through may be placed in the extraction cell, whicheffectively reduces the undesirable circular flow in the cell caused byCoriolis force, and the liquid jet of the mobile phase entering the cellmore effectively breaks up into droplets upon hitting the insert, due towhich the interface between the two phases increases.

The task was solved in the sense of the invention with the extractioncell according to claim 1.

The task set for the invention was also solved with the centrifugalpartition chromatograph according to claim 12.

Individual preferable embodiments of the invention are specified in thedependent claims.

The details of the invention are presented in connection withembodiments, with the help of drawings. In the appended drawings

FIG. 1 a shows an outline block diagram of an exemplary embodiment of acentrifugal partition chromatograph,

FIG. 1 b is a simulated image of the liquid flow in an extraction cellnot containing an insert, which illustrates the damaging remixing effectof the Coriolis force in the cell,

FIG. 2 a depicts an outline longitudinal cross-section imageillustrating a preferable embodiment of the tubular shaped extractionchamber of the extraction cell according to the invention,

FIG. 2 b depicts an outline lateral cross-section image of the tubularshaped extraction chamber of the extraction cell according to FIG. 2 a,

FIG. 3 is a simulated image of the liquid flow in an extraction cellcontaining the insert according to the invention,

FIG. 4 a depicts a longitudinal cross-section of a preferable embodimentof the liquid inlet plug according to the invention,

FIG. 4 b depicts a lateral cross-section of a preferable embodiment ofthe liquid inlet plug according to FIG. 4 a,

FIG. 5 a depicts a longitudinal cross-section of a preferable embodimentof the liquid outlet plug according to the invention,

FIG. 5 b depicts a lateral cross-section of the liquid outlet plugaccording to FIG. 5 a,

FIG. 6 a depicts a longitudinal cross-section of another preferableembodiment of the liquid inlet plug according to the invention,

FIG. 6 b depicts a lateral cross-section of a preferable embodiment ofthe truncated cone element according to FIG. 6 a,

FIG. 7 depicts a longitudinal cross-section of another preferableembodiment of the liquid outlet plug according to the invention,

FIG. 8 depicts a schematic image of a module containing the extractioncells according to the invention,

FIG. 9 depicts a schematic image of a rotor containing the modulepresented in FIG. 9 .

FIGS. 2 a and 2 b show outline longitudinal and lateral cross-sectionsillustrating a preferable embodiment of the tubular shaped extractionchamber 12 of the extraction cell 10 according to the invention.

The extraction cell 10 contains an extraction chamber 12 delimited by acell wall 12 c and accommodating the liquid stationary phase 30 á, andon its opposing sides it has a liquid inlet opening 13 b and a liquidoutlet opening 13 k serving to let in and out the liquid mobile phase 30m to be made to flow through the extraction cell 10. The material of thecell wall 12 c delimiting the extraction chamber 12 is preferablystainless steel, but other materials are also conceivable, such astitanium alloy, aluminium, PEEK (polyether ether ketone), Teflon, etc.

In the case of a preferable embodiment the extraction chamber 12 isconstructed as a tubular body. This embodiment of the extraction chamber12 is preferably produced using a waste-free production technology, suchas 3D printing or injection moulding or metal casting. PEEK ispreferably used in 3D printing, but naturally other materials may alsobe used, as is known to a person skilled in the art.

An insert 14 through which liquid may pass is positioned in theextraction chamber 12 according to the invention between the liquidinlet opening 13 b and the liquid outlet opening 13 k. In the context ofthe present invention an insert 14 through which liquid may pass meansan insert that has internal passages via which liquids are capable offlowing through the insert 14. The average diameter of the internalpassages of the insert 14, in other words the average diameter of theircross-section is 1-30 times, more preferably 1-20 times, and even morepreferably 4-10 times the average diameter of the mobile phase 30 mdroplets created when the mobile phase 30 m is made to flow in thestationary phase 30 á. The cross-section of the internal passages is notnecessarily circular. They may be square, rectangular, triangular or anyother irregular plane figure. In this case average diameter may beviewed as the diameter of a circle with an area equal to that of thearea of the plane figure.

In the case of a preferable embodiment the insert 14 contains one ormore elements that liquid may pass through chosen from the followinggroup: wound up net made from metal wire, fibrous woven textile, glasswool, steel wool, although other materials may also be used as isobvious for a person skilled in the art. In a given case the insert 14may be fixed to the cell wall 12 c, for example, by gluing, soldering,welding or by other mechanical fixing process. In the case of anotherexemplary embodiment the liquid inlet opening 13 b and the liquid outletopening 13 k are dimensioned so that the insert cannot pass through, anddue to this it is not necessary to fix the insert 14 within theextraction chamber 12.

With respect to its structure the insert 14 may have an irregularstructure (glass wool, steel wool), a regular structure (metal wire,metal grid), or be a bulk insert. The latter may be realised by using agranulate, spheres, and/or other granular materials.

In the case of an especially preferable embodiment, with the extractioncell 10 in its position in the centrifugal partition chromatograph 20,the insert 14 is selected so as to reduce the effect of the Coriolisforce occurring in the extraction cell 10 when in operation.

While providing the insert 14 through which liquid may pass, theextraction cell 10 is filled with liquid stationary phase 30 á, thenliquid mobile phase 30 m is made to flow through the stationary phase 30a in such a way that the mobile phase 30 m breaks up into droplets whenit penetrates the stationary phase 30 á. Following this the averagediameter of the droplets of the mobile phase 30 m penetrating thestationary phase 30 á and breaking up into droplets is determined. Thismay take place, for example, by experiment, on the basis of an imagerecorded of the inside of the extraction cell, or theoretically, withthe help of formulae. In a given case the droplets may also have anirregular shape, in this case the diameter of a droplet may be definedas having the same diameter as sphere with the same volume as thedroplet. In the case of a preferable embodiment the average diameter ofthe droplets of the mobile phase is determined on the basis of theStokes' law. During this the droplets inside the extraction cell 10 areconsidered to be spherical, the average diameter d of which may becalculated, with good approximation, using the following formula:

$d = \frac{9*v*\eta}{2*\Delta\;\rho*\omega*\omega*R}$

where v is the velocity of the mobile phase 30 m penetrating thestationary phase 30 á as compared to the stationary phase 30 á, η is theviscosity of the stationary phase 30 á, Δρ is the absolute value of thedifference in density between the stationary phase 30 á and the mobilephase 30 m, ω is the angular velocity of the rotation of the extractioncell 10, and R is the distance of the extraction cell 10 from the axisof rotation. Naturally other relationships may be used to calculate theaverage diameter of the droplets apart from the above formula, as isobvious to a person skilled in the art.

By using the information obtained about the average diameter of thedroplets, an insert 14 through which liquid may pass is provided thathas internal passages, and the average diameter of the passages is 1-30times, preferably 1-20 times, even more preferably 4-10 times theaverage diameter of the droplets.

In the case of a preferable embodiment an insert 14 is provided of asize so that its volume is 1-30%, preferably 1-20%, even more preferably2-20% of the volume of the extraction cell 10. The volume that theinsert 14 fills in the context of the present invention is the ratio ofthe net volume of the insert 14 and the internal volume of theextraction cell 10, where the net volume of the insert 14 is equal tothat volume of liquid a completely immersed insert 14 would push out ofa completely filled vessel.

The insert 14 presented above may be produced, for example, from a woundup net of metal wire, fibrous woven textile, glass wool, steel wool andfrom similar products, or a combination of them.

As a result of the effect of the insert 14 the circular flow of theliquid mobile phase 30 m entering the extraction chamber 12 is reduced,as due to its viscosity a large amount of force is required for its topass through the internal passages of the insert 14, which represent abraking resistance to the flow. This braking resistance is alwaysopposite to the direction of movement of the liquid, and its extent iscomparable to, or in a given case greater than, the extent of theCoriolis force occurring in the extraction cell 10, and in this way itreduces or completely extinguishes its effect. As the mobile phase 30 mis driven by the difference between the centrifugal force and thebuoyancy, which resultant force is greater than the Coriolis force, themobile phase 30 m entering the liquid inlet opening 13 b can continue toflow through the extraction chamber 12 all the way to the liquid outletopening 13 k, through which it leaves the extraction chamber 12 (seeFIG. 3 ).

A further preferred characteristic of the insert 14 is that the liquidjet of the mobile phase 30 m entering the extraction chamber 12 filledwith stationary phase 30 á more effectively breaks up into droplets whenhitting the insert 14, and significantly ripples after passing throughthe insert 14. Due to this effect the mixing between the mobile phase 30m and the stationary phase 30 á improves, and the transfer surfacebetween the two liquids increases.

In the case of a preferable embodiment one or more pits 15 ensuring thesecuring of the extraction cell 10 to the external supporting structure22 (see FIG. 8 ) are established on the external surface of the cellwall 12 c of the extraction chamber 12.

In the case of an especially preferable embodiment the extraction cell10 can be attached to the extraction chamber 12, it contains the liquidinlet plug 16 b according to FIGS. 4 a and 4 b which includes in it theliquid inlet opening 13 b and the liquid outlet plug 16 k according toFIGS. 5 a and 5 b which includes in it the liquid outlet opening 13 k.In this case the liquid inlet opening 13 b is established in the inletplug 16 b, and the liquid outlet opening 13 k is established in theliquid outlet plug 16 k. The liquid inlet plug 16 b and/or the liquidoutlet plug 16 k are fixed to the cell wall 12 c of the extractionchamber 12 preferably with a releasable connection, such as a screwthread. Naturally other releasable fixing methods (such as claspfixing), or non-releasable fixing methods (such as welding, soldering,gluing, riveting, etc.) may be used, as is known to a person skilled inthe art.

In a given case, an embodiment may be conceived in the case of which theliquid inlet opening 13 b is established in the liquid inlet plug 16 band the liquid outlet opening 13 k is established in the cell wall 12 c,or vice versa, in other words the liquid outlet opening 13 k isestablished in the liquid outlet plug 16 k and the liquid inlet opening13 b is established in the cell wall 12 c. The liquid inlet plug 16 band the liquid outlet plug 16 k are preferably made from one or more ofthe following list of materials: stainless steel, titanium alloy,aluminium, PEEK, Teflon. The liquid inlet plug 16 b and the liquidoutlet plug 16 k may also be made using one of the previously presentedwaste-free production technologies, and/or using other material workingtechnologies (such as milling, grinding, drilling, etc.).

The longitudinal and lateral cross-sections of a liquid inlet plug 16 bthat consists of a single part can be seen in FIGS. 4 a and 4 b . In thecase of a preferable embodiment the inlet plug 16 b leading the mobilephase 30 m into the extraction chamber 12 is established as acylindrical body, on the side of which facing the internal space of theextraction chamber 12 there is a thread 28 formed on the outside, suchas an external NPT(F) ⅜″ thread. In the case of this embodiment theextraction chamber 12 is established in the form of a tubular body, andat least at the one end of the tube on the internal surface there isalso a thread 28′ established, such as an NPT(F) ⅜″ thread, into whichthe NPT(F) ⅜″ thread 28 of the inlet plug 16 b may be screwed. Anexternal thread 29 is established at the other end of the inlet plug 16b, such as a 5/16-20 UN thread. Preferably a hexagonal nut formation maybe found between the NPT(F) ⅜″ and the 5/16-20 UN threads 28, 29, whichwhen held with a standard fork spanner the thread 28 of the inlet plug16 b may be easily driven into the thread 28′ of the extraction chamber12.

In the case of a preferable embodiment the liquid inlet opening 13 b ofthe inlet plug 16 b contains one or more slanted bores 17 f that dividesthe liquid flowing through it into several liquid jets (see FIGS. 4 aand 4 b ). In the case of an exemplary embodiment the diameters of thebores 17 f are between 0.1 mm and 1 mm, but naturally differentdiameters may also be conceived. The role of the bores 17 f is to dividethe jet of mobile phase 30 m liquid into several parts and to spray itevenly into the extraction chamber 12. The division may take place intoany optional number of branches, however, when producing the bores it ispreferable if the following aspects are taken into consideration:

-   -   when divided the flowing liquid should be divided in equal        proportions,    -   the liquid flowing in the various bores should take equally long        paths.

According to liquid simulation tests dividing the mobile phase 30 m intoseveral liquid jets has a positive effect on the flow pattern, asatomisation is improved, or, in other words, the interface between thetwo phases increases, which is especially desirable from achromatography point of view.

In the case of an exemplary embodiment the outlet plug 16 k is alsotubular, which, however, preferably contains a single branched liquidoutlet opening 13 k, and conical machining 17 k is formed on its sidefacing the internal space of the extraction chamber 12 (see FIGS. 5 aand 5 b ).

Similarly to the inlet plug 16 b, on the side of the outlet plug 16 kfacing the internal space of the extraction chamber 12 there is anexternal thread 28 formed on the outside, such as an NPT(F) ⅜″ thread,and on the other side there is an external thread 29 formed on theoutside, such as a 5/16-20 UN thread. The outlet plug 16 k may also befixed into the thread 28′ of the extraction chamber 12 using theexternal NPT(F) ⅜″ thread 28. The connection tube 18 visible in FIG. 9may be connected to the external 5/16-20 UN thread 29 of the inlet plug16 b and outlet plug 16 k, with the help of which a liquid connectionmay be realised between the liquid outlet opening 13 k of an extractioncell 10 and the liquid inlet opening 13 b of another extraction cell 10connected in series with it.

The purpose of the conical machining 17 k is for the droplets of themobile phase breaking up into droplets which pass through the extractionchamber 12 to easily combine, and due to this only the mobile phase 30 mleaves through the liquid outlet opening 13 k.

In the case the extraction chamber 12 has a larger tube diameter, theliquid inlet plug 16 b and/or the liquid outlet plug 16 k areconstructed from several parts that may be separated from each other, ascan be seen in FIGS. 6 a and 7. In the case of this embodiment theliquid inlet plug 16 b contains an inlet truncated cone element 19 bresponsible for the division of the liquid jet of the mobile phase 30 mand for sealing, a cylindrical body 19 h fitted to it, and a threadedcap 19 m fixing the cylindrical body 19 h to the extraction chamber 12.The material of the inlet truncated cone element 19 b is preferablyPEEK, but apart from this it may be made of Teflon, HDPE or othermaterial that is easily machined. The cylindrical body 19 h ispreferably made from ANSI 316 stainless steel, but it may also be fromtitanium alloy, aluminium, PEEK, Teflon, etc., as is obvious for aperson skilled in the art.

In the case of a preferable embodiment four branches are formed bymilling in the inlet truncated cone element 19 b, and three bores 17 fbranch off each branch, as can be seen in FIG. 6 b . Therefore, thereare a total of twelve bores 17 f located in the inlet truncated coneelement 19 b, through which the mobile phase 30 m gets into theextraction chamber 12 after being evenly divided. A section of internalsurface of the cell wall 12 c at the side towards the liquid inletopening 13 b is etched, which is followed by a conically shaped machinedsection into which the inlet truncated cone element 19 b fits so as toform a seal.

The cylindrical body 19 h contains a base part 19 t that is drilledthrough in the centre and fits into the internal machining of theextraction chamber 12 and a hollow stem 19 sz fixed to the base part 19t, as can be seen in FIG. 6 a . The inside of the stem 19 sz includes a45 degree conical part 119 and a 6.45 mm depression, a thread 27 ispreferably formed on its exterior surface, such as a 7/16-20 UNC thread,with the help of which the connection tube 18 may be fixed to the stem19 sz.

In the case of this embodiment a fine M60x3 metric thread is formed onthe external surface of the cell wall 12 c, at both ends of thecylindrical body shaped extraction chamber 12, onto which the threadedcap 19 m may be screwed. The edge of the threaded cap 19 m screwed ontothe extraction chamber 12 fixes the inlet truncated cone element 19 band the cylindrical body 19 h located in the extraction chamber 12. Thematerial of the threaded cap 19 m is preferably strong steel.

An embodiment is also conceivable in which the inlet truncated coneelement 19 b and the cylindrical body 19 h are fixed to the extractionchamber 12 with the thread formed on the external surface of thecylindrical body 19 h and the thread formed on the internal surface ofthe cell wall 12 c. In this case it is unnecessary to use a threaded cap19 m. The screwing in of the cylindrical body 19 h preferably takesplace using the hexagonal nut formation established on the cylindricalbody.

The construction of the liquid outlet plug 16 k according to FIG. 7differs from that presented above to the extent that instead of an inlettruncated cone 19 b it contains an outlet truncated cone 19 k, on whicha single branch liquid outlet opening 13 k and conical machining 17 kfacing towards the internal space of the extraction chamber 12 areformed.

FIG. 8 illustrates a module 40 of a rotor 24 according to the invention,which contains several extraction cells 10 connected in series withconnection tubes 18. In the case of this embodiment the module 40 alsoincludes in itself the supporting structure 22 that fixes the extractioncells 10 to the module 40. The module 40 is preferably fixed to therotor 24 in a releasable way, such as by using screws. The supportingstructure 22 is preferably of high strength and has a light, grid-likeor net-like structure. The supporting structure 22 may be constructedfrom, for example, metal, metal alloy, plastic, other composite, etc.,as is obvious for a person skilled in the art. The extraction chamber 12is fixed to the supporting structure 22 using one or more pits 15 formedin the external surface of the cell wall 12 c, preferably in areleasable way. Naturally, the extraction cells 10 may be fixed to thesupporting structure 22 in other releasable or non-releasable ways,apart from the fixing with the pits 15.

FIG. 9 illustrates a disc rotor 24 with an annular cross-sectionconstructed using the modules 40 presented in FIG. 8 . This embodimentof the centrifugal partition chromatograph 20 has a modular structuremade up of substantially identical modules, in the case of which each ofthe modules 40 contains one or more extraction cells 10 connected withconnection tubes 18 ensuring a liquid connection between them.

Around the circumference of the rotor 24 the modules 40 are connected inseries with connection tubes 18 in such a way that the liquid input of aselected module 40 is preferably connected to the liquid input at themain axis of the rotor 24 through a feed tube 26, while the liquidoutput of the neighbouring module 40 is preferably connected to theliquid output at the main axis of the rotor 24 through a discharge tube26′.

In the following the operation of the extraction cell according to theinvention and of the centrifugal partition chromatograph 20 containingthe extraction cell 10 is presented.

Before separation the extraction cells 10 are at least partially filledwith liquid stationary phase 30 á, then the rotation of the rotor 24along with the extraction cells 10 is started. Following this thepumping of the mobile phase 30 m through the series-connected extractioncells 10 is started and as a consequence of the rotation centrifugalforce occurs in them. This centrifugal force immobilises the stationaryphase 30 á, in other words it keeps the stationary phase 30 á in thecells. Subsequently, the mixture to be separated is added to the mobilephase 30 m with the sample input unit, preferably in impulse-like doses.

The direction of the pumping is selected as follows depending on therelationship between the densities of the stationary phase 30 á and themobile phase 30 m:

-   -   if the stationary phase 30 á is the denser phase (ascendant        mode), then the mobile phase 30 m is made to flow in the        direction of the axis of rotation of the rotor 24;    -   if the stationary phase 30 á is the less dense phase (descendent        mode), then the mobile phase 30 m is made to flow from the        centre of rotation in the direction of the rotational        circumference.

Due to the pumping the mobile phase 30 m enters the extraction cell 10via the liquid inlet opening 13 b, then breaks up into tiny droplets inthe stationary phase 30 á. In an ideal case the distribution of thedroplets is homogenous inside the extraction chamber 12. The insert 14placed in the extraction chamber 12 further improves the homogenisation.

Coriolis force is created in the extraction cells 10 of the rotatingrotor 24 as a result of the rotation, which endeavours to displace theflow of the mobile phase 30 m entering the extraction chamber 12 in thesideways direction. The insert 14 exerts resistance with respect to theflow, which resistance is comparable to the extent of the Coriolisforce, thereby significantly reducing its effect. As the differencebetween the centrifugal force and the buoyancy is exerted on the mobilephase 30 m, which resultant force is greater than the Coriolis force,the mobile phase 30 m entering through the liquid inlet opening 13 b isable to flow through the extraction chamber 12 containing the insert 14.In an ideal case the two phases are in contact with each other from theliquid inlet opening 13 b all the way to the liquid outlet opening 13 k.The mobile phase 30 m and the stationary phase 30 á become separated inthe proximity of the liquid outlet opening 13 k due to the conicalmachining 17 k and the effect of the difference in density between thetwo phases. The phase with lower density is driven by buoyancy towardsthe liquid inlet opening 13 b, while the denser phase continues to bemoved towards the liquid outlet opening 13 k due to the greatercentrifugal force being exerted on it. In an ideal case only the mobilephase leaves the extraction cell 10. The processes presented above arecarried out and repeated in each of the series-connected cells 10. Ifthe mixture to be separated is added to the mobile phase 30 m(preferably intermittently), then the components characterised bydifferent partition coefficients are separated from each other in theextraction cells 10.

In the case of a preferable embodiment several series-connectedextractions cells 10 form modules 40 that may be individually removedfrom the centrifugal partition chromatograph 20. One of the greatestadvantages of the modular construction is that in the case of a singleextraction cell 10 becoming faulty (blocked, for example) the extractioncell 10 can be easily repaired or replaced, furthermore, the periodicalcleaning of the extraction cells 10 is also simpler to perform. In thecase of those embodiments in which the liquid inlet opening 13 b and theliquid outlet opening 13 k are formed in the inlet plug 16 b and theoutlet plug 16 k, the cleaning of the extraction cells can be simplyperformed by unscrewing the plugs, as opposed to the solutions accordingto the state of the art, in which the entire device has to be dismantledto do this.

It is clear that alternative solutions will be apparent to a personskilled in the art as compared to the embodiments presented here, which,however, fall within the scope of protection determined by the claims.

The invention claimed is:
 1. An extraction cell (10) for a centrifugalpartition chromatograph (20), comprising an extraction chamber (12)delimited by a cell wall (12 c) which extraction cell (10) is suitablefor accommodating a liquid stationary phase (300, and has a liquid inletopening (13 b) and a liquid outlet opening (13 k) serving to let in andout a liquid mobile phase (30 m) to be made to flow through theextraction cell (10), which extraction cell (10) contains an extractionchamber (12) established as a tubular body, and a liquid inlet plug (16b) that includes a liquid inlet opening (13 b) and a liquid outlet plug(16 k) that includes a plurality of fluid delivery passages and a liquidoutlet opening (13 k), that can be attached to the extraction chamber(12), wherein an insert (14) through which liquids may pass ispositioned in the extraction chamber (12) between the liquid inletopening (13 b) and the liquid outlet opening (13 k), which has internalpassages, and the average diameter of the internal passages is 1-30times the average diameter of the liquid mobile phase (30 m) dropletscreated when the liquid mobile phase (30 m) is made to flow in theliquid stationary phase (30 á), wherein the insert (14) contains one ormore components that liquid may pass through selected from the groupconsisting of fibrous woven textile, glass wool, and steel wool.
 2. Theextraction cell (10) according to claim 1, which has been made by awaste-free production technology.
 3. The extraction cell (10) accordingto claim 1, wherein the insert (14) contains steel wool.
 4. Theextraction cell (10) according to claim 1, wherein the insert (14) has aporosity which is selected to reduce the effect of the Coriolis forceoccurring in the extraction cell (10) as a result of rotational movementof the extraction cell (10) when it is in the centrifugal partitionchromatograph (20) in operation.
 5. The extraction cell (10) accordingto claim 1, wherein the cell wall (12 c) delimiting the extractionchamber (12) is made of one or more of stainless steel, titanium alloy,aluminium, PEEK, and Teflon.
 6. The extraction cell (10) according toclaim 1, wherein the liquid inlet plug (16 b) and/or the liquid outletplug (16 k) are fixed to the cell wall (12 c) of the extraction chamber(12) with a releasable connection.
 7. The extraction cell (10) accordingto claim 1, wherein one or more pits (15) are present on an externalsurface of the cell wall (12 c) of the extraction chamber (12) to ensurefixing of the extraction cell (10) to an external supporting structure(22).
 8. The extraction cell (10) according to claim 1, wherein theliquid inlet plug (16 b) contains more than one bore (17 f) that dividea liquid made to flow through it into several liquid jets.
 9. Theextraction cell (10) according to claim 1, wherein the liquid inlet plug(16 b) and/or the liquid outlet plug (16 k) are constructed from severalparts that may be separated from each other.
 10. The extraction cell(10) according to claim 1, wherein the liquid inlet plug (16 b) and theliquid outlet plug (16 k) are made from one or more of stainless steel,titanium alloy, aluminium, PEEK, or Teflon.
 11. The extraction cell (10)according to claim 1, wherein the average diameter of the passages is4-10 times the average diameter of the liquid mobile phase (30 m)droplets created when the liquid mobile phase (30 m) is made to flow inthe liquid stationary phase (300.
 12. The extraction cell (10) accordingto claim 1, wherein the liquid inlet plug (16 b) and/or the liquidoutlet plug (16 k) are fixed to the cell wall (12 c) of the extractionchamber (12) with a releasable connection, which is a screw thread. 13.The extraction cell (10) according to claim 1, wherein the liquid inletplug (16 b) and/or the liquid outlet plug (16 k) are fixed to the cellwall (12 c) of the extraction chamber (12) with a releasable connection,which is a screw thread on a side of each of the inlet plug (16 b)and/or the liquid outlet plug (16 k).
 14. The extraction cell (10)according to claim 1, wherein the average diameter of the liquid mobilephase (30 m) droplets created when the liquid mobile phase (30 m) ismade to flow in the liquid stationary phase (30 á) is determined on thebasis of the following formula:d=9*v*η/2*Δρ*ω*ω*R wherein d is the average diameter v is the velocityof the liquid mobile phase (30 m) penetrating the liquid stationaryphase (30 á) as compared to the liquid stationary phase (30 á), η is theviscosity of the liquid stationary phase (30 á), Δρ is the absolutevalue of the difference in density between the liquid stationary phase(30 á) and the liquid mobile phase (30 m), ω is the angular velocity ofthe rotation of the extraction cell (10), and R is the distance of theextraction cell (10) from the axis of rotation.
 15. A centrifugalpartition chromatograph (20), comprising at least one extraction cell(10) according to claim
 1. 16. The centrifugal partition chromatograph(20) according to claim 15, which contains several extraction cells (10)that are connected in series with connection tubes (18) that ensure aliquid connection.
 17. The centrifugal partition chromatograph (20)according to claim 16, wherein the several series-connected extractioncells (10) together form one removable module (40).
 18. The centrifugalpartition chromatograph (20) according to claim 17, which has a modularstructure made up of substantially identical modules (40), where each ofthe modules (40) contains one or more extraction cells (10) connectedwith the connection tubes (18) ensuring a liquid connection betweenthem, furthermore, the individual modules (40) are connected to eachother in via the connection tubes (18).
 19. A method for providing theextraction cell according to claim 1 that may be used in a centrifugalpartition chromatograph (20), comprising providing serially connectedextraction cells (10) that are connected to each other by connectiontubes (18), filling the extraction cells (10) with the liquid stationaryphase (30 á), making the liquid mobile phase (30 m) flow through theliquid stationary phase (30 á), determining the average diameter of thedroplets of the liquid mobile phase (30 m) breaking up into droplets andpenetrating the liquid stationary phase (300, and arranging the insert(14) through which liquid may pass through in the extraction cell (10)that has internal passages, wherein the average diameter of the passagesis 1-30 times the average diameter of the droplets.